On the Potato Disease. 
373 
help again refeiTing to the testimony of M. Decaisne and other 
authorities on the Continent, that the weather was as I have 
before stated, wherever the disease was observed by them. And 
as to its occurrinof under glass, I will mention one case which I 
witnessed, in which, under a mistaken notion, a sudden change 
was admitted to a range of pits planted with potatoes, which were 
nearly destroyed in consequence. The proprietor informed me 
himself that these potatoes had only had wafer twice since they were 
planted (I believe he added in November, and I saw them in 
March, when they had potatoes as large as eggs upon them), and 
upon those occasions the lights were removed to admit sliowers of 
rain. To this, therefore, I attribute his loss, as well as to the 
fact that a great many squares of glass were broken. They had, 
in fact, received too sudden and copious a supply of air and water 
after having been for three months stinted of both : and this is 
not a solitary instance. Some grown close to these were perfectly 
healthy. 
To my mind, therefore, the sudden and extreme alternations 
of the weather last season, by imitating which as closely as cir- 
cumstances beyond my control would permit, I have artificially 
produced the same disease upon the potato this year, were of 
themselves quite sufficient to produce the late almost universal 
calamity ; for it has been shown that these causes prevailed gene- 
rally, not only in Europe, but in America also, on which con- 
tinent Mr. Robertson informs me that it is a well-known fact that 
the potato cannot be grown south of Washington, owing to the 
constant occurrence of such weather, and he further adds, 
*' Should we happen to be visited with the kind of climate that 
prevails south of that city, we must expect to experience the same 
results." And I entirely adopt these words in reference to our 
own country, and only beg leave to add to them, " and not other- 
wise.^ 
I should be sorry to say, however, that the disease could not be 
produced in any situation by other means than those which I 
have shown will induce it ; for, from my recent experiments, I 
am quite satisfied (and I know I do not stand alone) that it is not 
near so difficult a task to render a plant diseased as some persons 
may imagine, but there are plenty of cases in which the finest 
theories carried out by first-rate practic3 fail to produce a healthy 
condition. But no case has hitherto come to my knowledge for 
which J do not consider the causes I have assioned to have been 
amply sufficient. The plant having been rendered partially inert 
by the repellent action of cold, wet, and gloomy weather, uncon- 
genial to its nature as an exotic from a warm climate, at that 
critical period of its growth when in the course of ordinary seasons 
it would have been about to acquire strength and hardness, but 
